1. Field of the Invention
The present invention relates to an inkjet type image recording apparatus, and more specifically relates to the structure of a device for supporting a carriage carrying a recording head.
2. Description of Related Art
An example of the mainstream structures of conventional image recording apparatuses is the structure disclosed in Japanese Patent Application Laid-Open No. 5-270091 (1993) in which a carriage carrying a recording head is slidably supported by a guide shaft in the shape of a round shaft so that the carriage is movable reciprocally along the main scanning direction (hereinafter referred to as the “X-axis direction”, the X axis representing an axis extending in the main scanning direction).
Since the guide shaft in the shape of a round shaft has good dimensional precision and high rigidity, it is capable of decreasing the variation in a so-called paper gap from the nozzle surface of the recording head to the surface of a recording medium, and has the advantage of readily providing high-quality recorded images. However, this structure has the disadvantage of high costs including the frame structure, and also has the problem that it is very difficult to mount the carriage because it is necessary to first detach the guide shaft from the frame and then remove the carriage from the guide shaft when removing the carriage from the guide shaft, and it is necessary to execute the reverse procedure when mounting the carriage.
As a prior art for solving the above-mentioned problems, Japanese Patent Applications Laid-Open Nos. 2002-254746 and 2005-313492 disclose the structures in which the plate-like first guide member and second guide member are arranged lengthwise in the main scanning direction on the upstream side and downstream side of a plate-like platen in a paper transport direction (a sub-scanning direction orthogonal to the main-scanning direction (hereinafter referred to as the “Y-axis direction”, the Y axis representing an axis extending in the sub-scanning direction), a recording head is provided on the lower surface of a carriage supported slidably over the first and second guide members, and the carriage is connected to a part of an endless belt placed lengthwise in the main scanning direction so that it is moved reciprocally by a carriage drive motor.
Provided on the lower surface of the carriage is a guide section (slidable projection section) that comes into contact with a slide surface formed on the upper surface of each of the first and second guide members to control a print gap (paper gap) between the recording head of the carriage and paper on the platen. Moreover, on the guide member located closer to a position including the joint section with respect to the endless belt (the second guide member located on the downstream side), a carriage guide plate is formed to stand in a vertical direction (the Z-axis direction orthogonal to the X axis and the Y axis) so that, when the carriage is pulled and moved by the endless belt, the orientation of the carriage does not turn about the vertical (perpendicular) axis (hereinafter referred to as the Z axis).
The carriage disclosed in Japanese Patent Application Laid-Open No. 2002-254746 includes an ink cartridge. On the other hand, in an inkjet printer disclosed in Japanese Patent Application Laid-Open No. 2005-313492, an ink cartridge is placed in a stationary manner in the main body housing of a printer apparatus, and the ink cartridge and the carriage are joined with an ink supply tube.
By the way, as shown in Japanese Patent Application Laid-Open No. 2005-313492, a drive pulley is attached to a carriage motor (CR motor) fixed to the frame of the apparatus main body or one end of the second guide member in the main scanning direction, and a driven pulley is rotatably attached to the other end in the main scanning direction. The drive pulley and the driven pulley have a flange section formed to prevent the endless belt wound around these pulleys from being displaced in the axial direction of the pulleys.
However, at the initial stage at which the carriage is started moving along the main scanning direction (X-axis direction), that is, when acceleration is given to the carriage, a moment to rotate the carriage about an axis (Y axis) in the sub-scanning direction through the center of gravity acts. Thus, the posture of the carriage during an image recording operation is unstable, and the accuracy of the above-mentioned paper gap (hereinafter referred to as the “PG”) becomes unstable and causes problems that the quality of images to be recorded may be deteriorated or unstable.
Moreover, in the second guide member disclosed in Japanese Patent Application Laid-Open No. 2005-313492, since the slide surface for supporting the carriage (namely, a surface for controlling the gap dimension (PG) between the nozzle surface of the recording head and the platen), a reference surface with respect to the heights of the CR motor, drive pulley, driven pulley, etc., and a reference surface for the mount surface of a maintenance mechanism are substantially level with each other, it was impossible to adjust the height position of center of gravity of the carriage in the vertical (Z-axis) direction and the pulled height position of the endless belt (the height position of the belt joint section) to the most stable positions in the Z-axis direction.